Average Speed Check

sausage27 · Occasional Visitor Joined: Dec 13, 2006 Posts: 29

I regularly go through the 50 mph roadworks on the M25 (north) and about a month ago I noticed the speed on my 740 was showing 49 and not wavering, I normally set my speed to the satnav rather than the speedo.
I also noticed a line across the top of the number.

Initially I though the satnav had gone wrong but on clearing the last average speed camera it reverted to normal operation.
Kept a look out for it next time I went through and sure enough there is the line again. Sussed it was showing me my average speed (it came on at the first camera and off at the last)

But the last couple of times I've been through there it doesn't do it anymore.

Was this experimental? Has anyone else noticed it?

Peter

DennisN · Posted: Sun Sep 22, 2013 9:19 am Post subject:

Sounds like TomTom speed rather than your own speed. Do you have it set to show max speed alongside your speed, i.e. do you get two speeds showing, namely your speed with speed limit (according to TomTom) alongside it?

Do you have two speeds bottom left as in this screenshot and which one was doing the 49 with a line? The one on the right is TomTom speed limit and they did at one time seem to start showing the supposed average speed limit, but it was very flaky. It started doing it for my local M4/M5 set for a while, but then stopped (This is an ancient screendump, not recent and not of my local roadworks).

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layingback · Regular Visitor Joined: Feb 12, 2009 Posts: 124

The bar over the top is Average speed based on where TT thinks the cameras are/were.

As you go through the 1st camera (or TT's location of it ;-) ) the display disappears totally AT A VERY CRITICAL TIME for a few seconds, then reappears with the bar.

It's useful - BUT ONLY IF TT PLACED THE CAMERAS CORRECTLY - but it's UI could be improved. Eg. that delay at beginning is inexcusable (why take out the normal display if the average version isn't ready yet?), it is no help at the intermediate cameras, the current speed should still be displayed some where in a smaller font - because of those intermediate cameras eg, and a short freeze of the final average speed at the end would be good, so you can get a final check.

Overall a well overdue addition, but let's hope it's not TT's final rendition of this feature.
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Andy_P · Posted: Sun Sep 22, 2013 5:00 pm Post subject:

Confirmed - the figure with a bar over it is the calculated average speed you are doing throught the SPECs camera zone.
It's not a particularily new feature, my TomToms have been doing it for ages.

@layingback, I'm not sure why you're worried about the instantaneous speed disply disappearing momentarily as you enter the first camera or why you say the average speed display is of no use as you pass the intermediate cameras?

The SPECS cameras ONLY read your registration number and pass that to the system which works out your average speed. They do not measure your actual speed at the camera at all.
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layingback · Regular Visitor Joined: Feb 12, 2009 Posts: 124

M8TJT · Posted: Sun Sep 22, 2013 7:56 pm Post subject:

But TA don't calculate speed, they make maps. Apart from that, the instantaneous speed (velocity, actually) can be obtained from the satellite chipset to a high degree of accuracy. Having said that, the speed algorithm in the nav software could possibly use a 'weighted average'.

DennisN · Posted: Sun Sep 22, 2013 8:09 pm Post subject:

Unless there's been a change, I think you'll also find that TT's average speed is calculated from the start of the zone and is not recalculated between cameras on a multi-camera stretch.

For my local set, that caused real alarm - as I approached the junction (M5 to M4), there was a traffic holdup meaning that as I entered the zone I was doing about 5mph. It cleared very quickly, so that by the time the next camera came up, we were travelling freely. PGPSW's CamerAlert programme on my iPhone correctly recalculated my average from there, but the TT Live device was still calculating from when I started at 5mph - and showed my average as lower than it really was!
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layingback · Regular Visitor Joined: Feb 12, 2009 Posts: 124

psyskiesman · Posted: Mon Sep 23, 2013 2:24 pm Post subject:

If you were to treat the average speed cameras as fixed speed cameras you wouldn't have to worry about your average speed; in the 50mph average speed zone on the M5 just don't go over 50mph and you'll be ok! It's not like it's hundreds of miles in length; you'll only lose a couple of seconds by staying at 50mph maximum.

DennisN · Posted: Mon Sep 23, 2013 7:51 pm Post subject:

I can now confirm that today I got the speed with a line above it on M4 at Bristol 50mph average speed zone. The speed shown was different from (invariably lower than) the average speed shown in PGPSW's CamerAlert on my iPhone. I feel confident of the pgpsw figure based on past experience, although I have no personal means of checking either pgpsw or TT. On my first run through, the speed stayed constant 43mph all the way through. On my second run, I deliberately speeded up and nudged 50 to try and get it to show higher - CamerAlert did respond and edged up to average 48, the GO edged up from 43 to 44 - I guess I would have had to drive over 50 for some distance to get it anywhere near 50.

This only happened with my GO550 Live. It did not happen with my GO 1005 Live, nor with my Renault (TT) R-Link Live (but then, nothing happens with the Renault thing!!).
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M8TJT · Posted: Mon Sep 23, 2013 8:12 pm Post subject:

DennisN · Posted: Mon Sep 23, 2013 8:26 pm Post subject:

I always drive at or below the speed limit. I just like that nice lady talking to me every time a camera goes by!
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If it tastes good - it's fattening.

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JockTamsonsBairn · Posted: Mon Sep 23, 2013 11:10 pm Post subject:

M8TJT · Posted: Mon Sep 23, 2013 11:35 pm Post subject:

That's a rather selective quote Jock. Shocked

DennisN · Posted: Tue Sep 24, 2013 7:01 am Post subject:

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